This invention is based on and claims priority to Japanese Patent Application No. Hei 11-262482, filed Sep. 16, 1999, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
This invention relates to a lubrication system for an outboard motor engine, and more particularly to a sealing construction for a pump housing of a lubrication system for an outboard motor engine.
2. Description of Related Art
A typical outboard motor includes a drive unit and a bracket assembly. The bracket assembly is mounted on a transom of an associated watercraft and supports the drive unit. The drive unit carries a propulsion device, such as a propeller, which is normally placed in a submerged position. The propulsion device has a propulsion shaft. An internal combustion engine is employed for powering the propulsion device. The engine has a crankshaft. Because the engine is normally positioned atop the drive unit, a driveshaft extends between the crankshaft of the engine and the propulsion shaft so as to transmit engine output to the propulsion device.
The driveshaft is coupled with the bottom end of the crankshaft. A spline connection is usually applied to couple together the shafts. A lubrication system for the engine usually has an oil pump unit defined at this connection so that the crankshaft can drive the oil pump.
The outboard motor is surrounded by a body of water when used, and quite often uses the water for cooling the engine and an exhaust system. The shaft connection is exposed to the water. If the outboard motor is used at the sea, the water contains impurities such as salt. The impurities deposit on the connection between the driveshaft and the crankshaft and/or corrodes the connection, thereby causing the shafts to stick together, which makes it difficult to disassemble the shafts.
In order to avoid this situation from occurring, lubricant oil of the lubrication system can be used because the oil exists in the close proximity to the coupling portion. The lubrication system, however, has only a limited amount of oil due to a relatively small space the outboard motor. The oil for the lubrication system thus should not be applied for that purpose. If applied, however, the oil at the coupling portion must be removed when the entire oil is replaced. Otherwise, the oil that accumulates there will deteriorate.
Japanese Laid Open Patent Publication H04-295114 discloses a solution for the problem. A rotary oil pump is defined around a coupling portion of a crankshaft with a driveshaft. The oil pump includes a pump plate, a pump case depending from the pump plate and a seal housing. These three components substantially define a pump cavity that contains rotors driven by the crankshaft. The coupling portion between the shafts includes a sleeve which is press-fitted into a recess formed at the bottom of the crankshaft. The sleeve is internally splined. The driveshaft also is splined at its top end and is coupled with the sleeve. One seal member is provided between an inner surface of the seal housing and an outer surface of the sleeve. Another seal member is provided between an inner surface of the seal housing and an outer surface of the sleeve.
In this construction, however, the outer surface of the sleeve must be machined after being press-fitted into the recess for ensuring a sufficient seal. Manufacturing steps thus increase. In other words, manufacturing of the outboard motor becomes more costly.
A need therefore exists for an improved lubrication system that can inhibit water from entering a coupling portion of the crankshaft with the driveshaft and can use oil from a lubrication system without increasing the number of manufacturing steps.
In accordance with one aspect of the present invention, a lubrication system is provided for an internal combustion engine. The engine has a crankshaft extending generally vertically. A driveshaft also extends generally vertically and is driven by the crankshaft. The lubrication system comprises a pumping assembly driven by the crankshaft. A pump housing is arranged to contain the pumping assembly. The pump housing includes an inlet port through which lubricant enters the pump housing and an outlet port through which the lubricant is discharged from the pump housing. Both the crankshaft and the driveshaft extend through an opening defined at the pump housing and are coupled with each other within the pump housing. A first seal member is disposed around the crankshaft to seal a first location between an outer surface section of the crankshaft and a first inner surface section of the pump housing that defines at least a portion of the opening. A second seal member is disposed around the driveshaft for sealing a second location between an outer surface of the driveshaft and a second inner surface section of the pump housing that also defines at least a portion of the opening.
In accordance with another aspect of the present invention, an oil pump unit is provided for an outboard motor. The outboard motor has a driveshaft extending generally vertically and an internal combustion engine including an output shaft extending generally vertically. The oil pump unit comprises an upper housing section. A lower housing section is coupled with the upper housing section and defines, together with the upper housing section, an internal cavity adapted to contain lubricant. The driveshaft and the output shaft included engaged end portions that are coupled with each other in the internal cavity. A pumping assembly is disposed within the internal cavity and is driven by the output shaft. A first seal member is positioned between the output shaft and the upper housing member to inhibit the lubricant oil from leaking out of the internal cavity. A second seal member is positioned between the output shaft and the lower housing section to inhibit the lubricant oil from entering a location about the engaged end portions of the driveshaft and output shaft within the internal cavity. A third seal member is positioned between the driveshaft and the lower housing section to inhibit water from entering the location about the engaged end portions.
Further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiment which follows.